Novel FMCW-Interferometry Method Testing on an Ultrasonic Clamp-On Flowmeter

Abstract

Paper represents the extended version of the authors previous works on the transit-time ultrasonic flowmeters accuracy increasing problem. We deal with a new method of ultrasonic clamp-on transit-time flow measurements using the linear frequency modulated continuous wave (FMCW) signals and interferometry based time-of-flight (delay) estimation technique. The analog FMCW signals preprocessing is performed by the heterodyne based scheme of the receiver (the results are so-called the beat signals). A statistically effective time delay estimator for the digitized beat signal model is discussed. The algorithm for the flow velocity (thus the flow rate) measurement based on the proposed estimator is considered, which can be implemented on the modern microcontroller with the relatively high computation performance. The algorithm effectiveness was experimentally proved for the clamp-on ultrasonic liquid flowmeter in the cases of a well and relatively poor matching between the piezo-transducers and pipe material. Experiments show that the standard deviation ( i.e. , the square root of the variance) and the bias can be reduced at 7–10 times in comparison with the traditional FMCW signal processing techniques. Further, we consider application of our approach to a designed type of flowmeters based on the electromagnetic waves.